1. Field of the Invention
The present invention relates to a rice cooking method, and more specifically it relates to a rice cooking method whereby, in the soaking step for water absorption prior to the cooking of rice, the rice is soaked in water containing water-soluble hemicellulose, or powdered water-soluble hemicellulose is sprinkled over the washed rice and mixed therewith for complete coverage after which water is added in an amount sufficient for water soaking; this method allows the soaking time to be shortened, and allows larger amounts of rice than usual to be cooked without changes in quality or texture from cooking the rice when an excess of water is added during the cooking.
2. Description of the Related Art
Rice has long been cooked in large amounts on a daily basis at restaurants for many different purposes, such as for rice balls, sushi, curry rice, bowl rice, fried rice, etc., and such cooked rice must always be of a consistent quality. For example, when nonglutinous rice is cooked, the rice can usually be obtained at a consistent quality by cooking it under prescribed conditions, but in order to obtain rice of consistent quality, by cooking under prescribed conditions after washing polished rice is usually subjected to soaking treatment in which sufficient water is added into the rice.
Specifically, when using large-scale automatic rice cookers which generally have the capacity for 500-4000 portions per hour, rice has been prepared through a series of steps comprising a step of washing polished rice (stored rice), a step of soaking the washed rice in water, a step of draining the soaked rice and a step of adding cooking water to the drained rice, followed by a step of rice cooking and a step of steaming; however, traditionally it has been necessary for the washed polished rice (hereunder also referred to as "washed rice") to be combined with an equivalent or an excess of water for soaking of the washed rice. Depending on the type of rice, the washed rice can usually absorb from 1.25 to 1.30 times its weight in water, and this has necessitated a very long period of 1.5 to 3.0 hours for soaking, thus constituting the greater part of the preparation time from polished rice to cooked rice. This has made it difficult to lower preparation costs and resulted in very poor operating efficiency.
For steamed rice with red beans (okowa) it is common to use glutinous rice alone or glutinous rice in admixture with nonglutinous rice, but sufficient absorption of water by glutinous rice usually requires soaking overnight, and thus the working time is longer than for nonglutinous rice. Consequently, it is impossible to satisfy unexpected orders, and early preparation is particularly necessary for year-end rice cakes, making it very difficult to deal with any sudden orders. For this reason, modifications have been made to the mechanical working steps in order to shorten the soaking time, such as adjustment of the soaking temperature, or subjection to reduced pressure for rapid permeation of water into the rice; however, when the soaking temperature is raised in order to increase water absorption efficiency, swelling of the starch particles leads to rupture of the starch particles during the cooking stage after soaking, so that the shape of the rice grains cannot be maintained and the rice tends to stick together. Also, when the soaking is carried out under reduced pressure, there is a risk of cracking (splitting) of the rice grains, whereby the rice grains are destroyed and the quality of the cooked rice is impaired.
For commercial mass preparation of rice, a simple method is also employed using pregelatinized rice wherein a portion of the starch has been gelatinized by first heating polished rice with water vapor in order to eliminate the soaking step; however, such rice is generally expensive, and increases the preparation costs for large-scale commercial rice cooking. Also, since pregelatinized rice has a high moisture content prior to cooking, it has poor storage qualities and the texture of the cooked rice is notably impaired when it is stored for long periods, so that it is not practical as rice for convenience stores and the like where rice is kept for extended periods prior to sale.
In addition, when the rice is cooked using an excess of water with respect to the rice, the rice grains are destroyed and the characteristic light stickiness and elasticity of the rice is lost, giving it a heavy stickiness. If instead the amount of water is reduced the starchy grains of the rice cannot be fully gelatinized, producing hard, non-sticky rice which has lost all value as a food product. Consequently, while the amount of water used during cooking cannot be generally standardized due to the differences in rice types and rice age, it is normal to cook rice with an amount of water most suited to the type of rice and the conditions for the rice cooking, and rarely is rice cooked with larger amounts of water added for the purpose of improving rice yields, that is, with the rice cooked in an excess amount of water to increase the volume of the rice.